This a request for investigation and development of a diagnostic tool to assess platelet function; the instrument will utilize a laser light.scattering method to detect platelet aggregates in blood. Current platelet aggregometers assess platelet aggregation either in media free of erythrocytes, or an indirect approach is used to extrapolate information relating to platelet aggregation. The applicants have tested the feasibility of utilizing the light-scattering concept for detection of platelet aggregates in the presence of all blood cells (whole blood). The promise shown by preliminary results has prompted the efforts for development of a whole blood aggregometer. Platelet aggregometers can be found in nearly all reasonably equipped hemostasis laboratories; they are widely used to examine platelet function in the blood of patients with abnormal hemostasis. The applicants anticipate that the light-scattering whole blood aggregometer will greatly facilitate the performance of aggregation tests, it will be more cost-effective, and minimize the risk of operator contact with blood. It will assess platelet function in more physiologically relevant conditions and it has the potential of being more sensitive in its ability to detect platelet abnormalities. The work will entail development of a suitable sample chamber, optimization of signal detection scheme and proper algorithms for data processing and display of results. PROPOSED COMMERCIAL APPLICATIONS: This research will lead to the development of a device which will have applications in clinical laboratories. The device will test the functional status of blood platelets and help in identifying abnormalities in these cells. The device will permit assessment of platelet function in undiluted whole blood; this is not possible with the existing aggregometers.